Hollow bar



NITED STATES PATENT OFFICE.

EDIVARI) I.. CLARK, OF PITTSBURG, PENNSYLVANIA.

HOLLOW BAR.

SPECIFICATION forming part of Letters Patent No. 456,646, dated July 28,1891.

Application tiled January 26, 1891. Serial No. 379.101.V (No model.)

To all whom it may concern,.-

Be it known that I, EDWARD L. CLRK, of Pittsburg, in the county ofAllegheny and State of. Pennsylvania, have invented a new and usefulImprovement in Spiral Hollow Bars, of which the following is a full,clear, and exact description. My invention relates to an improvement inbars or rods of metal adapted to be used for fence-posts, am? for othertratcd in the accompanying drawings, in which- Figure l is a plan Viewof a rod embodying my invention. Fig. is a longitudinal axial sectionthereof, and Fig. 3 is a cross-section on the line III III of Fig. l.

The article shown in the drawings is a hollow rod made by twisting intospiral forma strip ot' metal (iron or steel) preferably with l suiieienttightness to cause the edges to meet .seas to forni the spiral ridge.

purposes where a strong light structure is required. It is illusand bycontinuing it they exert pressure on each other and are thereby bentoutwardly, The bar thus produced is lightin weight, butis remarkablystrong and rigid, being able to resist great strains and beingespecially adapted to bcemployed for making fence-posts and for `otherpurposes which will be suggested to those skilled in the art. p

My inventiongbroadly considered, is not limited to the rod with thespirally-projecting rib, but will cover described, but without bringingthe edges together with. suflicicnt tightness to produce the rib.

l. As a new article of manufacture, a metal rod composed of a spit-allywound and twisted strip of uniform thickness having a projecting spiralrib at the meeting edges, substantially as and for the purposesdescribed.

2. The method herein described, which consists in twisting a strip ofmetal when cold into spiral form, bringing thereby its edges intocontact, and bypressure of contactforming a. projecting spiral rib,substantially as and for the purposes described.

In testimony whereof I have hereunto set my hand this 24th day ot'Januar QA. I). 1891.

E DWARD L. CLARK.

'Witnesse THOMAS W. lLuurwaLL, W. I Conwix.

a hollow rod made as above

